In an environment where calories were scarce and hunger was a constant threat, sugar provided an enormous survival advantage. Naturally occurring sugars such as fructose and glucose offered a dense, immediate source of energy. More importantly, fructose is uniquely effective at signalling to the human body to store fat. When seasonal fruit ripened, overeating it allowed early humans to build a life-saving layer of fat before the beginning of winter or the dry season. Individuals who sought out and consumed the most sugar were more likely to survive periods of…